1. Field of the Invention
The present invention relates to automatic and accurate method and apparatus capable of detecting flaws mainly in circumferential weld zones of pipe lines.
2. Description of the Prior Art
X-ray penetration testing has conventionally been applied for non-destructive inspection of weld zones. In conjunction with the improved performance of ultrasonic flaw detection apparatus, the application of ultrasonic flaw detection methods and techniques have recently been required for improved detection accuracy, shortened detection time, safe operation and decreased detection costs. In particular, in the non-destructive inspection of circumferential weld zones for high-pressure pipe lines, such weld zones have been inspected by the combined use of X-ray penetration testing and ultrasonic flaw detection techniques. Ultrasonic flaw detection has been performed mainly manually. However, manual ultrasonic flaw detection requres considerable skill and experience for the discrimination of the jamming echoes due to the weld bead, from the flaw echoes and also requires considerable technical skills. Under certain operational conditions, weld flaw detection has to be performed under severe conditions at sites such as common workshops where other operations are also being performed. Such conditions present intolerable burdens to the welding operations and inspectors.
In order to overcome such problems, it is desirable to automate welding flaw detection methods and techniques and also the associated necessary data processing, such as recording and evaluation and the like of the detected results.